Prostate cancer is second only to lung cancer as a leading cause of cancer death in men in the United States, where one out of every six men are affected by the disease during their lifetime. Currently, prostate cancer is screened using serum prostate-specific antigen (PSA) screening. As the test is presently unreliable, patients who are deemed at risk undergo biopsy under real-time 2D transrectal ultrasound (TRUS) guidance. Because potential cancer cells are almost always indistinguishable from normal prostate tissue under ultrasound, the procedure is performed in a systematic but random manner over the entire gland. During “sextant biopsy”, the most common form of TRUS biopsy and current standard of care, one or more biopsies are obtained from each of six zones that the prostate is divided into and analyzed.
Sextant biopsy is widely used due to its low cost and simplicity relative to other methods of detecting prostate cancer but has been shown to have a significant false negative rate, which has been shown to be higher for lesions located in the anterior or apical prostate. The results of sextant biopsy are commonly reported in text format alone, or at best, using a crude rough standard map of the prostate on which biopsy results are manually annotated by the pathologist.
In some cases, cancers may be seen under one or more volumetric imaging methods or sequences such as Magnetic Resonance Imaging (MRI), diffusion weighted imaging, dynamic contrast enhanced MRI, MR spectroscopy, or other volumetric data scanning (ultrasound elastography, ultrasound thermometry, or spectrum analysis of raw radiofrequency signal from ultrasound transducer). Regression analysis of multi-parametric imaging volumetric data weighs each imaging parameter and assigns a relative risk value to each image or data type in order to assign a total risk for each voxel (roughly between 100 microns and 5 mm). Voxel analysis may be performed on voxels of different sizes or by re-sampling based upon borrowed features from neighboring voxels, or upon any algorithm that weighs the various MRI sequences and raw radiofrequency ultrasound signal to assign a risk for cancer to each voxel. The spectrum of the raw ultrasound signal is then analyzed, and referenced to a library or look-up table for cancer risk at any voxel location (which are based upon prior RF signal or imaging to tissue correlation). In these cases, it is desirable to sample the lesion seen on MRI using biopsy to confirm the existence of and evaluate the type of cancer. The result of the biopsy may then alter treatment decisions. The current state of the art does not allow easy targeting of a biopsy needle into a potential cancer site seen under MRI once the patient has been moved out of the MRI. While possible to perform the intervention in the MRI magnet itself, this is time consuming and costly.
In addition, it is sometimes desirable to perform minimally invasive, nerve sparing or organ preserving therapy on the prostate using techniques such as cryotherapy or laser ablation that preserve at least part of the prostate and thereby minimize the chance of severe complications that sometimes accompany surgery to remove the entire gland. By precisely targeting focal cancer lesions, surgery that spares the gland for at least the short term, may be possible. Additionally, in low dose brachytherapy, it would be ideal if radioactive seeds placed in the prostate can be clustered in the area where most of the lesions are found. All of these treatment modalities are typically used for localized and image-able prostate cancer, typically on patients who might otherwise undergo “active surveillance” or “watchful waiting” for a slow growing and photogenic prostate cancer, such as cases where the Gleason score is less than 7.
Image guided procedures are well known in the art and use a position sensor such as an optical or electromagnetic tracking system to determine the location and orientation of an instrument such as a biopsy probe or of an imaging device such as a hand-held ultrasound probe or fluoroscopy device, CT fluoroscopic scanner gantry, etc. in a coordinate system. When performing an image guided biopsy it is sometimes important to record the geometric location and orientation of the imaging device if used, and the biopsy device (as determined by the position sensor). It may also be helpful to capture a video image or several images from the imaging device at the time the biopsy is taken. This enables recording of the precise origin of a biopsy which is especially important in cases where the target is small. By knowing the position of an abnormal sample, it may be possible to target treatment to the abnormal tissue, or conversely, to spare healthy tissue.
Current biopsy devices lack an integrated electronic sensor, such as an electrical switch, that can be used by software associated with the position sensor to determine the precise instant at which the biopsy is taken. This makes it difficult to record an image and position data at the exact time of biopsy, since no electronic trigger is available. Instead, paper or verbal notes may be taken or a video/data recording may be taken by the imaging system to capture a plurality of sequential video frames. Of the many hundreds of frames that are captured in just a few seconds, only one or two may show the actual biopsy being performed with the rest being of little value. It is therefore difficult and time consuming, and may involve complicated video image analysis software to obtain the video location of the biopsy. Once the correct video frame has been located it then is necessary to correlate the position sensor data taken at the same time as the video to locate the same time point in the data stream. Only then is it possible to obtain the quantitative position and orientation data of the biopsy. This too may be time consuming or involve collection and processing of a large amount of data.
A signal at the time of biopsy may be obtained by using a switch within the biopsy probe. However, this may be costly and complicated to implement given that the biopsy probe is typically an inexpensive mechanical device and does not normally contain electronics. Such a switch also is not required for many simple biopsies that do not involve computer assisted image guided surgery, and would only add to the cost of the device.
With regards to performing prostate therapies, the current state of the art uses a transperineal approach in which a plate contains a plurality of holes into which needles are inserted. The needles may contain radioactive seeds for use in brachytherapy, cryogenically cooled probes, or thermal therapy probes in which heat is applied to all or portions of the prostate in order to ablate or otherwise treat the organ. The needle may be placed using guidance from imaging modalities such as transrectal ultrasound, intraoperative MRI fused MR/US, PET/CT or other modalities or combination thereof. In some cases it is preferable to perform the therapy using a transrectal needle approach rather than a transperineal method. In these cases a needle may be inserted using an imaging modality such as an MRI scanner or a transrectal ultrasound (TRUS) probe to help guide the needle.
Numerous TRUS needle guides are available, such as those manufactured by Civco Inc. (Kalowna, Iowa), for example the “613-246 Sterile endocavity needle guide for Philips C9-5ec transducer”. This class of device is removably attached to the TRUS transducer and houses a tube or channel into which a biopsy or other needle may be inserted. The orientation and position of the needle guides of the same type remains repeatable each time it is re-attached to the transducer.
The channel and thus the needle path has a fixed orientation relative to the scan plane of the transducer, enabling the ultrasound supplier to “predict” the path of the needle and apply an overlayed graphic line to the anatomical image from the ultrasound to help guide the needle to the correct location. This line represents the needle path if it were to be extended. Furthermore, the needle channel is placed directly in the field of view of the imaging array of the transducer, so that the needle can be directly viewed as it is extended out of the needle guide.
Current ultrasound needle guides are sufficient to perform transrectal biopsies but are not designed for transrectally applied therapy. In performing therapy, there may be advantages to inserting a treatment needle transrectally instead of through the perineum. These include the application of the therapy using a well-established workflow that closely follows that of prostate biopsy. In these cases, the needle is inserted through the rectal wall and the therapy applied. During application of the therapy, it is critical to be able to visualize and image all aspects of the gland.
In a prior art needle guide, a biopsy needle 104 is placed through a needle guide 100 such as shown in FIG. 1. Needle guide 100 contains a housing 101, that may be removably attached to an ultrasound transducer such as a TRUS transducer (not shown). Needle guide 100 also contains a tube 102 into which a functional needle such as a biopsy needle 104 is inserted. In this prior art needle guide, biopsy needle 104 is slideably and axially constrained to tube 102, i.e. biopsy needle 104 may only be slid up and down tube 102 or axially rotated along its length. Once a needle is inserted into tube 102 and exits the end hole 103, and into tissue 105, the transducer that is also attached to the needle guide may not be reoriented (except for an axial spin as note above) or repositioned to better visualize the therapy without removing the needle from the tissue. Thus, the ultrasound probe must remain in place while the therapy is applied. If the action of the therapy cannot be directly and completely viewed by the ultrasound transducer in this position, the therapy cannot be properly monitored. With the needle in place the transducer is effectively “pinned” to a location and may not be freely moved to view the progress and extent of the therapy.
Furthermore, it may be necessary to place more than one functional needle to effectively apply the therapy, for example in Irreversible Electroporation (IRE), multi-pole radiofrequency ablation, cryotherapy etc. Again the prior art does not allow this to be performed. It may also be necessary to use additional functional needles to effectively monitor the therapy, e.g. thermal sensors such as thermocouples. Again, prior art does not allow for this possibility.
In these cases, it is highly desirable to disengage one or more needles from the TRUS probe after placement, allowing for better monitoring of the needle's location, subsequent therapy and/or to allow the positioning and placement of subsequent needles.
Accordingly there exists a need to solve these and other problems to facilitate minimally invasive needle procedures in the prostate. For example, there is a need to facilitate minimally invasive transrectally applied needle procedures in the prostate while allowing the physician to move and reorient a transducer. There is also a need to facilitate the placement of devices at specific targets as determined using MRI, Positron Emission Tomography (PET), Computed Tomography (CT) or other volumetric scan techniques, but with the assistance of low cost and convenient imaging systems such as TRUS. There is also a need to facilitate the collection of data during image guided procedures and treatments.